Seamless Steel Pipe

The production processes of seamless steel pipes are divided into two types: cold drawing and hot rolling:

The production process of cold-rolled seamless steel pipes is generally more complex than that of hot-rolled ones. The pipe billet first undergoes three-roll continuous rolling, followed by sizing testing after extrusion. If no corresponding cracks appear on the surface, the round pipes are cut by a cutting machine into billets about one meter in length. Afterwards, they enter the annealing process, during which pickling is carried out with acidic liquid. Attention must be paid to whether a large number of bubbles form on the surface during pickling; excessive bubbles indicate that the steel pipe fails to meet the corresponding quality standards. In terms of appearance, cold-rolled seamless steel pipes are shorter than hot-rolled ones. They generally have thinner wall thicknesses, yet feature a brighter and smoother surface with less roughness and fewer burrs at the pipe ends.

Hot-rolled seamless steel pipes are usually delivered in the hot-rolled state after heat treatment. After quality inspection, they are strictly manually screened by workers, followed by surface oil coating. Multiple cold drawing tests are then conducted consecutively. Perforation tests are performed after hot rolling, and straightening correction is required if excessive perforation and diameter expansion occur. After straightening, the pipes are transported by conveying devices to flaw detection machines for non-destructive testing. Finally, they are labeled, sorted by specifications, and stored in warehouses.